/**
 * 发送get异步请求
 * @param {string} url 请求地址
 * @param {object} params 请求数据
 * @param {string|undefined} type 返回数据类型
 * @param {object} headers 自定义请求头
 * @returns promise
 */
function get(url,params,type,headers){
    const p = new Promise((resolve,reject) => {
        const xhr = new XMLHttpRequest
        xhr.onreadystatechange = () => {
            if(xhr.readyState === 4){
                if(xhr.status === 200){
                    let res = xhr.responseText
                    if(type === 'json') res = JSON.parse(res)
                    resolve(res)
                }else{
                    reject(xhr.status)
                }
            }
        }
        let temp = []
        for(let key in params)
        {
            temp.push(`${key}=${params[key]}`)
        }
        xhr.open('get',`${url}?${temp.join('&')}`)
        for(let key in headers)
        {
            xhr.setRequestHeader(key,headers[key])
        }
        xhr.send(null)
    })
    return p
}



/**
 * 发送post异步请求
 * @param {string} url 请求地址
 * @param {object} params 请求数据
 * @param {string|undefined} type 返回数据类型
 * @param {object} headers 自定义请求头
 * @returns promise
 */
 function post(url,params,type,headers){
    const p = new Promise((resolve,reject) => {
        const xhr = new XMLHttpRequest
        xhr.onreadystatechange = () => {
            if(xhr.readyState === 4){
                if(xhr.status === 200){
                    let res = xhr.responseText
                    if(type === 'json') res = JSON.parse(res)
                    resolve(res)
                }else{
                    reject(xhr.status)
                }
            }
        }
        let temp = []
        for(let key in params)
        {
            temp.push(`${key}=${params[key]}`)
        }
        xhr.open('post',url)
        xhr.setRequestHeader('content-type','application/x-www-form-urlencoded')
        for(let key in headers)
        {
            xhr.setRequestHeader(key,headers[key])
        }
        xhr.send(temp.join('&'))
    })
    return p
}